JPH08250277A - High frequency heating apparatus - Google Patents

Abstract

PURPOSE: To improve heating efficiency by driving a matching element in a wave guide and forming the optimum matching for every food. CONSTITUTION: A matching element supporting axis 13 made of ceramic is penetrated in a point which is eccentric from a center line in a heating chamber side of a wave guide 5 in the way it can rotate freely and a matching element 10 composed of a circular base 11 and a stub 12 is installed inside the wave guide 5. An directivity coupling apparatus 6 is attached to the wall of the wave guide 5 positioned between a magnetron 3 and the matching element 10. A control apparatus 15 drives a rotary drive apparatus 14 after heating is started and at the same time stores detection signals of the directivity coupling apparatus 6, determines the optimum stopping position of the rotary drive apparatus 14 among the detection signals, and rotates and drives the matching element supporting axis 13 to the determined position. The control apparatus finds the optimum second rotary angular position in a range of rotary angles back and forth on a first rotary angle position as a center during the heating period after the start and rotates and drives the matching element supporting axis 13 and fixed the axis 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency heating apparatus for adjusting impedance matching between a magnetron and a heating chamber based on a detection signal of a directional coupler mounted on a waveguide wall. More specifically,
During the heating period, the magnetron was made to operate at maximum efficiency all the time.

[0002]

2. Description of the Related Art As a conventional high-frequency heating device of this type,
For example, as in the invention of Japanese Patent Application Laid-Open No. 57-23494, a part of the inner wall of a waveguide connecting a magnetron and a heating chamber is provided with microwaves at an interval of 1/4 of the wavelength inside the tube of microwaves to be transmitted. 3 impedance adjustment rods are installed along the traveling direction of each, and the impedance is adjusted by using a driving device so that the operating point of the magnetron approaches the maximum power region on the Rieke diagram for each food item installed in the heating chamber. In addition to controlling the amount of protrusion of the rod in the pipe, the amount of protrusion for each food item is stored, and the stored content is recalled and used according to the food item so that the heating operation is performed at the highest heating efficiency. Proposed.

[0003]

In the above-mentioned conventional example, three impedance adjusting rods, which are matching elements, must be arranged in the waveguide at an interval of 1/4 of the in-tube wavelength. Since a driving device is required for each impedance adjusting rod, the structure becomes complicated. In addition, because the adjustment rod must take measures against leaked radio waves in the part that penetrates the waveguide wall,
There is a problem that the structure becomes larger and larger, and it is difficult to apply to a high-frequency heating device such as a microwave oven, which is strongly required to be downsized. In addition, the decrease in reliability,
There was also a problem that a large increase in cost was unavoidable.

In addition, in the above-mentioned conventional example, it takes a long time because the impedance adjusting rods are drive-controlled to perform matching as a high-frequency heating device.
There is a problem in that it is not practical in a consumer device such as a microwave oven that must complete heating in a short time.

Further, since the impedance adjusting rod does not move other than the previously memorized operation, it is difficult to obtain optimum impedance matching for various foods having different shapes and different dielectric characteristics, and also during heating. It has a fatal drawback that it cannot cope with a shift in the impedance operating point that changes.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and includes a heating chamber for storing food, a magnetron for oscillating microwaves outside the heating chamber, and one side. At the wall of the rectangular rectangular waveguide, a rectangular waveguide connecting the magnetron and the heating chamber on the other side and connecting the magnetron and the heating chamber on the other side, It is installed at a position between the connection part with the magnetron and the connection part with the heating chamber, detects the incident and reflected components of the microwave power transmitted in the rectangular waveguide, and outputs their detection signals. Rotating to a position closer to the heating chamber than the position where the directional coupler and the directional coupler on one wall of the rectangular waveguide are attached, and which is offset from the center line of the radio wave traveling direction of the wall. The matching element supporting shaft made of a low dielectric loss material is pierced through, the matching element made of a conductive material is rotatably driven by being mounted on the matching element supporting shaft in the rectangular waveguide, and the matching element is A disk base concentrically attached to the matching element support shaft for configuring,
A stub made of a conductive material, which is provided at a position deviated from the center of the disc base, and a matching element support shaft are rotationally driven for a predetermined stroke outside the rectangular waveguide, and are predetermined in the drive stroke. And a rotation drive device that outputs information about a plurality of rotation angle positions, and when the high frequency power supply device is activated to start the oscillation of the magnetron, the rotation drive device is activated to rotate and drive the matching element support shaft. To capture and store the detection signals of the directional coupler for each of a plurality of predetermined rotational angle positions during the drive stroke and to determine the optimum stop position of the rotary drive device from the stored detection signal groups. To find a specific detection signal in the detection signal group, drive the matching element support shaft to the detected first rotation angle position of the detection signal, and rotate the matching element support shaft at a predetermined position during the subsequent heating period. At that time, the matching element support shaft is rotationally driven within the range of a predetermined rotation angle before and after the first rotation angle position, and the direction of each of a plurality of predetermined rotation angle positions during the driving process. In addition to capturing and storing the detection signal of the sex coupler, a specific detection signal in the detection signal group is found out from the stored detection signal group to determine the optimum stop position of the rotation drive device, and the detection is performed. A high-frequency heating device is configured with a control device that controls the rotation driving device so that the matching element support shaft is rotationally driven and fixed to the second rotation angle position where the signal is detected.

At this time, in order to find the second rotation angle position, the range of angles in which the matching element support shaft rotates back and forth around the first rotation angle position is used to find the first rotation angle position. The matching element support shaft should be smaller than the range of the angle of rotation.

[0008]

When the high frequency power supply device is operated to start the oscillation of the magnetron, the control device controls the rotary drive device to rotationally move the matching element support shaft for a predetermined stroke, and the drive stroke is predetermined. Capture the output signals of the directional coupler at a plurality of rotational angular positions and store them. The control device finds one detection signal from the stored signal groups that determines that the magnetron and heating chamber are in the best coupled state, that is, a detection signal that is determined to have impedance matching, and determines the drive device. The matching element supporting shaft is controlled and moved to that position (first rotation angle position). Then, at a predetermined time point during the subsequent heating period, the matching element support shaft is rotationally driven within the range of a predetermined rotation angle before and after the first rotation angle position, and the matching element support shaft is predetermined during the drive stroke. In addition to taking in and storing the detection signals of the directional coupler for each of the plurality of rotation angle positions, in order to determine the optimum stop position of the rotation drive device from the stored detection signal groups, When a specific detection signal is found, the matching element support shaft is rotationally driven and fixed to the second rotation angle position where the detection signal is detected. That is, the matching element support shaft is rotationally driven so as to correspond to the change in the property of the food due to the progress of heating.

When the matching element support shaft rotates back and forth about the first rotation angle position in order to find the second rotation angle position, the matching element support shaft detects the first rotation angle position. Rotates in a range smaller than the range of the rotated angle.

According to the present invention, since the matching element support shaft and the disc base are mounted at positions deviated from the center line of the waveguide wall in the radio wave traveling direction, when the matching element support shaft is rotated. The stub of the above-mentioned stub moves in a relatively large electric field strength region in the central portion of the waveguide over a relatively large rotation angle, that is, over a relatively long distance. This has a great influence on the change in the degree of coupling in the heating chamber. Further, the above-described structure acts similarly to the single stub tuner used as the matching element of the transmission line, and contributes to the realization of matching in a wider range.

Further, the disk base and the stub are driven on the load side as viewed from the magnetron, and the directional coupler detects incident and reflected power components between the magnetron and the matching element. Measurement of each reflected power and impedance matching are performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIGS. Reference numeral 1 is a metal heating chamber, and 2 is a high-frequency power supply port provided on the side wall of the heating chamber 1. 3 is a magnetron, 4 is a high frequency power supply device for driving the magnetron 3, 5 is connected to the magnetron 3 on one side and is connected to the heating chamber 1 on the other side to heat the high frequency power generated in the magnetron 3. It is a rectangular waveguide that is transmitted to the high frequency power supply port 2 of the chamber 1 and connects the magnetron 3 and the heating chamber 1. Reference numeral 6 denotes a directional coupler, which is composed of a double-sided printed wiring board, and is oscillated from the magnetron at approximately the center of the long side of the waveguide 5, that is, in the middle of the connection between the magnetron 3 and the heating chamber 1. It is mounted so as to be exposed to both the high frequency power that goes to the heating chamber 1 and the high frequency power that returns from the heating chamber and returns. 7
Is a conductor loop portion for detecting microwaves in the waveguide 5 by a loop coupling method, 8 is a microstrip line for transmitting a signal relating to microwave power coupled by the conductor loop portion 7, and 8a of these is a waveguide Reference numeral 5b denotes a microstrip line that transmits a signal related to incident power in microwave power that transmits 5, and reference numeral 8b denotes a microstrip line that also transmits a signal related to reflected power. Reference numeral 9 is a processing circuit for receiving, detecting and smoothing the microwave transmitted to the microstrip line 8 (8a, 8b). Reference numeral 10 is a matching element mounted in the waveguide 5, 11 is a disk base made of a conductive material, and 12 is a conductive material provided so as to project to a biased portion deviated from the rotation center of the disk base 11. The disk base 11 is rotationally driven in the waveguide so that impedance matching between the heating chamber 1 and the magnetron 3 is achieved. The outer diameter W is set to approximately 1/4 of the in-tube wavelength of the microwave transmitted in the waveguide 5. Although not shown, the stub 12 is detachably attached to the disc base 11, and the stub 12 having a different shape and size is prepared. There is an advantage that the unit such as the rotation drive device 14 can be easily applied to various high frequency heating devices having different specifications.

The matching element support shaft 13 is shown in FIG. 4 and FIG.
, A low dielectric loss material (ceramics) rotatably attached to the wall of the waveguide 5 at a position deviated from the center line of the wave propagation direction of the waveguide, and its lower end in the waveguide. The disk base 11 is attached to the.
Reference numeral 14 is a rotation driving device such as a stepping motor for rotating the matching element supporting shaft 13 to control the rotation angle. Reference numeral 15 is a control device connected to the directional coupler 6, the rotary drive device 14 and the high frequency power supply device 4, and is composed of a microcomputer. And 16 is food,
17 is the saucer.

In the thus constructed apparatus, when the food 16 is placed in the heating chamber 1 and the oscillation of the magnetron 3 is started, the high frequency power passes through the waveguide 5 and the heating chamber 1
Is supplied to the inside and the dielectric heating of the food 16 is started.

Then, the control device 15 first determines the drive device 14
Is controlled to rotate the matching element support shaft 13 about a predetermined angle of, for example, 180 degrees, that is, 1/2 rotation.
Actually, the driving is performed so that the stub 12 mounted at a position deviated from the rotation center of the disc base 11 moves more in the region where the electric field strength of the center line of the waveguide 5 wall in the radio wave traveling direction runs. , The driving stroke is defined.

Then, the control device 15 takes in output signals relating to the incident and reflected electric powers of the directional coupler 6 at a plurality of predetermined driving positions (rotational angle positions) during the rotational drive stroke, and outputs the respective rotational angle positions. Voltage standing wave ratio (VS
Remember them as the value of WR). The control device 15 finds one detection signal (minimum value of the voltage standing wave ratio) that determines that the magnetron 3 and the heating chamber 1 are in the best coupled state from the stored signal groups, The detected rotation angle position of the matching element support shaft 13, that is, the rotation drive device 1
The drive position (first rotation angle position) of No. 4 is confirmed, and the drive device 14 is controlled so that the matching element support shaft 13 is stopped and fixed at the drive position.

And at a predetermined point during the subsequent heating period,
For example, whether the heating mode is thawing frozen food, reheating cold cooked food to edible temperature, or full-scale cooking such as cooking rice or simmering food. After a predetermined time accordingly, within the range of a predetermined rotation angle before and after the first rotation angle position (specifically, from the range rotated to find the first rotation angle position) The matching element support shaft 13 is rotationally driven within a small range (within a relatively small angle range of 5 degrees before and after the first rotation angle position), and a plurality of predetermined plurality of predetermined angles during the driving stroke are driven. The detection signals of the directional coupler for each rotation angle position are fetched and stored, and specific detection in the detection signal group is performed to determine the optimum stop position of the rotation drive device from the stored detection signal group. Belief Heading its second matching element support shaft to the rotational angular position detected in the detection signal is rotated and fixed. That is, the matching element support shaft 1 is so arranged that the matching state is maintained corresponding to the change in the property of the food as the heating progresses.
3 is repeatedly rotated to the optimum position. As a matter of course, it goes without saying that the second optimum rotation angle position may be the same as the first optimum rotation angle position. Further, when the first rotation angle position is the end of the rotation drive range for finding the first rotation angle position, the rotation motion for searching for the second optimum rotation angle position is naturally restricted. As will be understood, in the present embodiment, the best matching position is found within the restricted range.

The rotational angle position at which the optimum coupling state is obtained here is such that the reflection coefficient obtained from the input and reflected power values detected by the directional coupler 6 is the minimum and the incident power is the maximum. Is the position.

The reason for doing so is that the magnetron does not necessarily operate at the maximum output just because the reflection coefficient value is small, and it may even be far below the rated output. This is because the operating characteristics are taken into consideration. That is, it is not possible to operate the magnetron 3 at the true maximum output only by focusing on the reflection coefficient. Therefore, in the present invention, the magnetron 3 is operated at the highest efficiency by finding the point (position) at which the incident power becomes the maximum at the minimum reflection coefficient. In the present invention, after performing this, and at a predetermined time point during the heating period thereafter, the matching element within a predetermined rotation angle range before and after the first rotation angle position. While rotating the support shaft, find the optimum second rotation angle position for alignment from the range of the predetermined rotation angle, and rotate and fix the alignment element support shaft to the second rotation angle position. I did it. And thereby
The magnetron was operated at the highest efficiency so that a better alignment was maintained in response to changes in food properties as heating progressed.

The stub 12 is different from the case where the matching element supporting shaft 13 is provided without being offset with respect to the center line of the waveguide.
Can be positioned in the region where the electric field strength is large in the region in which the center line of the wave propagation direction of the waveguide 5 wall runs, so that it exerts a greater influence on the matching adjustment, that is, the adjustment of the coupling degree. I was able to do it.

In the above description, only the case where the matching element support shaft 13 is rotationally driven has been described, but if the protrusion amount into the waveguide 5 is further controlled, finer control can be performed. Will be possible.

[0022]

As described above, according to the present invention, since the directional coupler and the matching element are sequentially mounted on the load (food) side as viewed from the magnetron, the efficiency of incident and reflected powers by the directional coupler is extremely high. It is possible to perform both good measurement and extremely efficient coupling of the magnetron and heating chamber with matching elements. In addition, the stub can be moved within a region in the waveguide where the electric field strength is relatively large.
Then, the detection signals of the directional coupler for each of a plurality of predetermined drive positions during the process are stored, and the drive that achieves the best impedance matching between the heating chamber and the magnetron from among the stored detection signal groups. Since the position (first rotation angle position) was found and the matching element was immediately moved to the position, the oscillation operating point of the magnetron moved to the matched and highly efficient operating point in a short time, It has become possible to perform high-frequency heating with good efficiency. Further, at a predetermined time point during the subsequent heating period, the matching element support shaft is rotationally driven within a predetermined rotation angle range before and after the first rotation angle position, and the predetermined rotation angle range is also set. The optimum second rotation angle position for alignment was found from among the above, and the matching element support shaft was rotatably driven and fixed at that second rotation angle position. Even if a change occurs, an excellent matching state can be maintained and a highly efficient heating operation can be maintained. Above all, it has become possible to greatly contribute to reducing adverse effects on the life of the magnetron.

[Brief description of drawings]

FIG. 1 is a conceptual configuration diagram of an embodiment of the present invention.

FIG. 2 is a plan view of one surface side of the directional coupler used in the present invention.

FIG. 3 is a perspective view of a matching element used in the present invention.

FIG. 4 is a partially cutaway perspective view of a waveguide having a matching element attached thereto.

FIG. 5 is a top view of the waveguide ceiling with the matching element attached.

[Explanation of symbols]

 1 Heating Chamber 3 Magnetron 4 High Frequency Power Supply Device 5 Waveguide 6 Directional Coupler 7 Conductor Loop 8 Microstrip Line 9 Processing Circuit Section 10 Matching Element 11 Disc Base 12 Stub 13 Matching Element Support Tool 14 Drive Device 15 Control Device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Fumimasa Anan, 2-82 Watanabe-dori, Chuo-ku, Fukuoka-shi, Fukuoka Kyushu Electric Power Co., Inc. (72) Kazuhiko Kimoto, Watanabe-dori, Chuo-ku, Fukuoka, Fukuoka 1-82, Kyushu Electric Power Co., Inc.

Claims (2)

[Claims] 1. A heating chamber (1) for accommodating food (15)
And a magnetron (3) that oscillates microwaves outside the heating chamber, and connects the magnetron on one side and the heating chamber on the other side to connect the magnetron and the heating chamber. A rectangular waveguide (5),
A high frequency power supply device (4) for driving the magnetron,
Incident and reflection of microwave power transmitted in the rectangular waveguide, which is mounted on the wall of the rectangular rectangular waveguide between the connection with the magnetron and the connection with the heating chamber. A directional raw coupler (6) for detecting each directional component and outputting those detection signals, and a heating chamber side from a position where the directional coupler is attached to one wall of the rectangular waveguide. Moreover, a matching element support shaft (13) made of a low dielectric loss material rotatably attached to the wall at a position deviated from the center line of the radio wave traveling direction.
And a matching element (10) made of a conductive material, which is attached to the matching element supporting shaft and driven to rotate in the rectangular waveguide.
A disk base (11) concentrically attached to the matching element support shaft to form the matching element, and a stub made of a conductive material projecting at a position deviated from the center of the disk base. (12) and a rotary drive device that rotationally drives the matching element support shaft outside the rectangular waveguide for a predetermined stroke and outputs information regarding a plurality of predetermined rotational angle positions during the drive stroke ( 14), and when the high frequency power supply device is activated to start the oscillation of the magnetron, the rotary drive device is activated to rotationally drive the matching element support shaft and a predetermined time during the drive stroke. The detection signals of the directional coupler for each of a plurality of rotation angle positions are captured and stored, and the optimum stop position of the rotation drive device is determined from the stored detection signal group. For detecting a specific detection signal in the detection signal group for rotationally driving the matching element support shaft to the detected first rotation angle position of the detection signal, at a predetermined time point during the subsequent heating period The matching element supporting shaft is rotationally driven within a range of a predetermined rotation angle before and after the first rotation angle position, and the directional coupling for each of a plurality of predetermined rotation angle positions during the driving process. And stores the detection signals of the detector and finds a specific detection signal in the detection signal group to determine the optimum stop position of the rotary drive device from the stored detection signal group and detects the detection signal. A high-frequency heating device comprising: a controller (15) for controlling the rotation driving device so as to rotationally drive and fix the matching element support shaft to a second rotation angle position where a signal is detected. 2. The range of the angle at which the matching element support shaft rotates back and forth around the first rotation angle position when finding the second rotation angle position means the first rotation angle position. The high-frequency heating device according to claim 1, wherein the matching element support shaft has an angle smaller than an angle range in which the matching element support shaft rotates when the matching element support shaft is found.